1. Field of the Invention
The present invention relates to an adjusting apparatus of a vibrating gyroscope, and more particularly to an adjusting apparatus of the vibrating gyroscope for obtaining the gyroscope having a good characteristics.
2. Description of the Prior Art
FIG. 3 is a perspective view showing an example of a vibrating gyroscope, and FIG. 4 is a sectional view thereof. The vibrating gyroscope 10 includes, for example, a regular triangular prism shaped vibrating body 12. The vibrating body 12 is formed, generally, by a material which generates mechanical vibration, such as elinver, iron-nickel alloy, quartz, glass, crystal, ceramics and the like.
At center portions on three side faces of the vibrating body 12, piezoelectric elements 14a, 14b and 14c are formed. The piezoelectric element 14a includes a piezoelectric layer 16a consisting of, for example, a piezoelectric ceramic. On both faces of the piezoelectric layer 16a, electrodes 18a and 20a are formed. One electrode 20a is bonded to the side face of the vibrating body 12. Similarly, the piezoelectric elements 14b, 14c include piezoelectric layers 16b, 16c, on the both faces of which electrodes 18b, 20b and electrodes 18c, 20c are formed. The electrodes 20b, 20c of the piezoelectric elements 14b, 14c are bonded to the side faces of the vibrating body 12.
Supporting members 22a and 22b are fixed to a ridge line near two nodal points of the vibrating body 12. The supporting members 22a and 22b are formed by bending metal wires into a U shape. Center portions of the supporting members 22a and 22b are welded to the ridge line of the vibrating body 12. End portions of the supporting members 22a and 22b are secured to a supporting plate 24.
In such vibrating gyroscope 10, when designating the ridge line between the piezoelectric elements 14a and 14b is taken as C, the ridge line between the piezoelectric elements 14a and 14c as L, and the ridge line between the piezoelectric elements 14b and 14c as R, the piezoelectric elements 14a, 14b on both sides of the ridge line C are used for detection and drive, and the piezoelectric element 14c is used for feedback. When using the vibrating gyroscope 10, a oscillation circuit is connected between the piezoelectric elements 14a, 14b for drive and the piezoelectric element 14c for feedback, and a drive signal is applied to the vibrating gyroscope 10 from the oscillation circuit. The vibrating body 12 bends and vibrates in a direction perpendicular to the face of the piezoelectric element 14c by the driving signal.
In this state, output signals from the piezoelectric elements 14a and 14b used for detection are equal and the difference is zero when measured. When the vibrating body 12 rotates on its axis, a vibrating direction changes due to a Coriolis force, and thereby the output signals differ between the piezoelectric elements 14a and 14b. Thus, when the difference of the output signals between the piezoelectric elements 14a and 14b is measured, a rotational angular velocity can be detected.
In such vibrating gyroscope 10, since detection of the rotational angular velocity is unstable when the biased vibration is generated due to the driving direction, frequencies in the respective vibrating directions are adjusted by cutting the ridge lines of the vibrating body 12. In this case, first, the oscillation circuit is connected between the piezoelectric elements 14a, 14b on both sides of the ridge line C and the piezoelectric element 14c, thereby the vibrating body 12 bends and vibrates in the direction perpendicular to the face of the piezoelectric element 14c. A resonance frequency Fx at that time is measured. Similarly, a resonance frequency Fy 1 is measured by connecting the oscillation circuit between the piezoelectric elements 14a, 14c on both sides of the ridge line L and the piezoelectric element 14b, and a resonance frequency Fy2 is measured by connecting the oscillation circuit between the piezoelectric elements 14b, 14c on both sides of the ridge line R and the piezoelectric element 14a. The ridge lines of the vibrating body 12 are cut so as to bring the differences between the resonance frequencies Fx, Fy1 and Fy2 within zero Hz to several Hz. By adjusting the resonance frequencies in the vibrating directions in such a manner, the vibrating body 12 can be vibrated stably and a good characteristics can be obtained.
However, in the vibrating gyroscope, there is not only the difference in resonance frequencies, but also output fluctuations of the detecting piezoelectric elements due to the temperature variations are encountered. When such drift due to a temperature variation is large, the vibrating body vibrates unstably to detect the rotational angular velocity erroneously, nevertheless there is no rotational angular velocity.